Numerous interventions in the medical area, for therapeutic as for diagnostic purpose, require access to the vascular system (veins or arteries). Access is obtained by direct puncture of vessels through the skin with a needle. Needles are usually made of a hollow tube, which is usually metallic and is beveled at one end (the distal end) and embedded in a plastic (and transparent) or metallic hub- or base-body on the other end (the proximal end).
Puncture is most of the times “blind”, except for venipuncture at the forearm/wrist level where veins can often be seen if compression is applied to the arm, above the puncture site. Otherwise vessel puncture is guided by palpation of the pulse, for artery, or by the supposed anatomic location for deep veins (e.g. jugular or femoral veins).
The success of vessel puncture relies in the outward flow of blood through the needle. For intra-venous drug or fluid injection, puncture of the vein is in general accomplished with a system made of a plastic tube (“cannula”) sliding over a hollow metallic needle: as soon as blood flows outside the hub- or base-body of the metallic needle, the plastic cannula is inserted more deeply in the vein, over the metallic needle which is removed thereafter. The cannula can now be attached to a perfusion system with a standardized connection, for example a “luer-lock” connection.
This kind of system (metallic needle+plastic cannula) can also be used for artery access, but most of the time, another technique is in use: the bare metal needle punctures the vessel, then the next step consists of pushing gently a tiny soft and floppy wire (preferably metallic with or without a hydrophilic coating) within the artery lumen through the hollow cavity of the needle. Guided by the wire laying in the lumen of the artery, the needle may be afterwards withdrawn and a material device comprising a plastic tube (“introducer” or “sheath”) overlaying a longer and distally tapered plastic tube (“dilator”) is inserted over the wire in the lumen of the vessel: it is the <<Seldinger>> technique.
In all cases, the blood outward flow at the base-body of the needle is the sign of a successful vascular access. However the observation of the blood in the base-body can be delayed, particularly for small vessels and in case of low vascular pressure (as in the veins, in general) or when working with long needles or small diameter needles. Thus, despite a correct access into the vessel lumen, the operator will continue to search the vessel and move inadvertently the needle . . . . This can result in an unsuccessful or painful or traumatic and/or hemorrhagic vascular access. Obtaining a quicker visualization of the blood outward flow in order to facilitate and make safer the operator's task of blood vessel puncturing therefore is desirable. Techniques to allow observation of blood after the puncturing a blood vessel include the <<basic>> technique of using transparent hub at the base of the needle, but also more elaborated ways as making aperture(s) or window(s) through the needle and to overlying tubes, making channels between different overlying tubes and using transparent material.
For example, the documents US 2008/0262431 and US 2008/0262430 describe a system firstly comprising a needle and secondly a dilator, disposed on and slideable along the body of the needle and thirdly, a medical article (a sheath), at least partially made of clear, translucent material, which is disposed on and slideable along the dilator. The needle itself has at least one aperture/fenestration (of any shape/length), as the dilator itself: through these apertures, the blood entering the lumen of the needle will flow into space/channel(s) created between the dilator and the sheath. Several ways of creating space between the dilator and the sheath are described, as by modifying the overall circumferential shape (rounded or oval, e.g.) either of the outer surface of the dilator or the inner surface of the sheath, or as by creating ridges along the outer surface of the dilator or the inner surface of the sheath.
The document US 2003/0153874 describes a vascular access system which comprises firstly a needle with at least one opening proximally positioned, secondly a transparent dilator having an annular recess therebetween, the dilator having a passage-way so that the dilator is coaxially positioned around the needle. Thirdly and optionally, a sheath, also transparent fits coaxially over the dilator and there is opening through the dilator allowing the blood to flow from the dilator to an annular space between the dilator and the sheath. The blood may flow through an optional side port in connection to the dilator. The system also uses a guidewire forwarded within the lumen's vessel through the lumen's needle. The dilator and the sheath are preferably clear, semi-opaque or translucent so that the operator can see the blood when blood flows into needle and then through opening into an annular space between needle and dilator, or into or through spaces in the dilator, or through an opening into an annular space between dilator and sheath.
The document WO 2007/070584 describes a needle with a transparent or translucent portion. This document describes a needle in which the inner member is made of metal or other opaque material and the outer member has a transparent or translucent portion. The inner member has one or more openings that permit the uses to visualize what is in the inner member, i.e., blood or medicine. These two tubes may be joined together to form one needle, although in various embodiments, they can act as either single or double lumen needles. The needle according to this document is employed to gain access to blood vessels for introduction of a medical device, e.g., a cardiac catheter for angioplasty.
The document U.S. Pat. No. 5,704,914 describes a system allowing visualization of the blood through a transparent/clear hub since this system comprises rigid clear plastic so that blood can be observed therein upon successful penetration of the lumen of a blood vessel by the needle tip. The system uses also a guidewire to be forwarded through the lumen's needle.
Unfortunately, such devices do not provide a permanently correct detection of blood directly viewable between said needle and said plastic sheath (cannula) since said external surface of the needle may stick against said internal surface of said sheath (cannula) and so prevent the passage of blood. Moreover, according to the documents US2008/0262431, US2008/0262430 and US2003/0153874, said apertures allowing visualization of blood are located both in the dilator and at the level of said needle, requiring some re-direction of the blood flow thereby delaying the visualization and increasing the final size of the apparatus, making the apparatus not suitable for access of small calibre vessels.